The use of catalytic alkylation processes to produce branched hydrocarbons having properties that are suitable for use as gasoline blending components is well known in the art. Generally, the alkylation of olefins, such as butenes, by isoparaffins, such as isobutane, is accomplished by contacting the reactants with an acid catalyst to form a reaction mixture, settling said mixture to separate the catalyst from the hydrocarbons, and further separating the hydrocarbons, for example, by fractionation, to recover the alkylation reaction product. Normally, the alkylation reaction product is referred to as “alkylate”, and preferably contains hydrocarbons having 7-9 carbon atoms. In order to have the highest quality gasoline blending stock, it is preferred that hydrocarbons formed in the alkylation process be highly branched.
Due to the increased use of shale crude and tar sands, refiners must now accommodate a growing amount of normal paraffins, such as n-butanes and n-pentanes in the feedstock. Finally, some refineries are trying to manage an increasing amount of light olefin byproducts, such as propylene, produced in existing fluid catalytic cracking (FCC) units.
There is a need for a more flexible process that can accept these feeds without requiring additional isobutane from an external source.